<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script type="text/javascript" src="/static/js3/jQuery-2.1.4/jquery-2.1.4.min.js"></script>
    <script>
        $(function () {
            var btnEle = document.querySelector('#btn');
            var $btn = $('#btn');
            var $btn = jQuery('#btn');
            console.log($btn);
            console.log($btn);
            console.log(btnEle);
            console.log($(btnEle));
            console.log($btn.get(0));

            var $btn = $(btnEle);
            var btnEle = $btn.get(0);
        })
    </script>
</head>
<body>
<button id="btn">切换显示</button>
</body>
</html>